I depends on what you are trying to do with your diet, athletes do one thing, weightlifters another and dieters usually try to find a low carb, high protein mix they can live with. When I first joined fitday I found out that I generally (even when dieting) tend to have a very heavily carb based diet (around 65% carbs), which I think has likely been the cause of my obesity. So for me to lose weight I do better and can eat more calories if I can keep the carbs lower than 50% and my proteins over 30%. My goal pie chart is 40% carbs, 40% proteins and 20% fats. Usually I'm at closer to 45% carbs, 35% proteins and 20% fats, but that works okay too.